Field
This disclosure is generally related to location determination using mobile devices. More specifically, the disclosure is related to techniques that do not rely on GPS for location determination.
Related Art
Mobile positioning via a mixture of GPS, cell towers, and previously mapped RF transmitters, e.g. WiFi access points, is commonly available. Such positioning is usually only accurate to approximately 7-25 meters—but can be 250 meters off in failure cases. Further, indoor environments tend to be poor for GPS reception, necessitating reliance on other mechanisms. One mechanism for improving reception is to make use of cell towers, e.g. use information about signal intensity from multiple known cell towers to triangulate an approximate location (200-1000 m accuracy). Another approach is to use a database of known WiFi transmitters, or other unregulated radio frequency (RF) transmitters.
For example, Skyhook Wireless provides software-only location mapping with about 10-20 meter accuracy using a database of known WiFi access points, GPS satellites and cell towers to compute a location. A core requirement for services like Skyhook Wireless is a reference database of WiFi access points. This database must be generated manually, e.g. via field surveys, manual data entry. Other companies such as Apple make use of the GPS in mobile devices to record a WiFi base station. These databases themselves must be regularly maintained and updated to provide good accuracy. Maintenance of such databases can require expensive monitoring equipment, trained field teams to survey locations, and regular updates. Additionally, such approaches do not address changing signal environments due to crowded-vs-empty areas, or changing signal conditions due to obstruction of the mobile devices' antenna(e) by the users' hands as the user changes the way in which he/she is holding the mobile device.
Still other approaches for indoor location determination such as those using ray tracing propagation models for indoor signal strength modeling, Sparse Extended Information Filter and GraphSLAM based approaches, or those approaches based on dead reckoning require prior information about the shape, layout, and sometimes materials of the location, e.g. shape priors. This approach can work if there are pre-existing maps and shape information that an authoritative source can provide. However, such an approach is often too computationally complex to run within the constraints of a mobile device or does not always work well in changing, or dynamic, environments.
Accordingly, what is needed is a method and apparatus for location determination on mobile devices without the need for prior information about the location, e.g. information about either the space itself or the unregulated RF transmitters/transmissions in the space.